1. Field of the Invention
This invention relates to a mobile unit communication system for providing communication between a base station and a plurality of mobile units within a service area.
2. Description of the Prior Art
A first prior art mobile unit communication system for providing communication between one of base stations and a plurality of mobile units within a service area of the base station through the Time Division Multiple Access/Time division Duplex (TDMA/TDD) method is known. In the Time Division Multiple Access, a plurality of channels are, i.e., the multiple access is, provided by using a radio wave through time-division. Therefore, a plurality of mobile units in a service area of a base station can communicate with the base station substantially at the same time. Time Division Duplex means that the reception of data and transmission of data are switched by time-division, i.e., the reception of the data and the transmission of data are effected alternately.
A second prior art mobile unit communication system for providing communication between one of base stations and a plurality of mobile units within a service area of the base station through the Code Division Multiple Access/Time division Duplex (CDMA/TDD) method is proposed in "POWER CONTROL IN PACKET SWITCHED TIME DIVISION DUPLEX DIRECT SEQUENCE SPREAD SPECTRUM COMMUNICATIONS", by R. ESMAILZADEH, M. NAKAGAWA, A. KAJIWARA, proc. of VTC '92, PP.989-992, 1992. In the Code Division Multiple Access, a plurality of channels are, i.e., the multiple access is, provided by using a radio wave through spread-spectrum with different coding signals for spread-spectrum. Therefore, a plurality of mobile units in a service area of a base station can communicate with the base station at the same time. Time Division Duplex means that the reception of data and transmission of data are switched by time-division, i.e., the reception of the data and the transmission of data are effected alternately.